Title: Probabilistic multifactorial lifetime assessment for resin-based composite restorations Abstract: While the development of the next-generation dental composites to extend the service life of tomorrow's dental restorations is underway, producing a rigorous tool that can better discriminate the many composite restorative systems by more accurately predicting their clinical performances is necessary. The long term goal of this project is to increase the lifetime of resin-base composite restorations by obtaining more durable restorative systems through a better understanding of the degradation mechanisms of the tooth-composite interface. Our more immediate goal is to develop a comprehensive and complementary analytical-experimental approach for predicting the lifetime of composite restorations. We would like to test the hypotheses that (1) the different mechanical, thermal, chemical and biological challenges work synergistically to reduce the lifetime of resin-based composite restorations; (2) we can predict the lifetime of composite-restored teeth using numerical stress analysis and a multi-factorial failure model; and (3) we can devise an accelerated test method with representative challenges that reproduce the failure rates and failure modes seen in composite-restored teeth clinically. We propose to conduct a series of laboratory and theoretical studies including 1) to develop and implement a multifactorial probabilistic model for failure prediction; 2) to determine the material properties pertinent to the failure model for commercial composites subjected to calibrated representative biomechanical challenges; 3) to predict the lifetime of different types of composite restorations (Class I and II) for premolars and molars using the failure model and the interfacial stresses predicted by Finite Element Analysis; 4) to design and build a microbiomechanical artificial mouth (BAM) by adding a biofilm reactor to an artificial mouth based on the existing design at the Minnesota Dental Research Center for Biomaterials and Biomechanics (MDRCBB) to simulate the microbiological and mechanical challenges in the oral environment; and 5) to develop an accelerated test regime using the multifactorial failure model together with a continuously increasing load. This research will introduce a comprehensive and quantitative approach to the structural analysis and lifetime prediction of composite dental restoration, validated by comparison with clinical results. It will assess degradation of the tooth-restoration interface under representative preparation and oral conditions, and the results will help elucidate the individual and synergistic effects of two main oral challenges, namely microbiological and biomechanical, and those of operator error on its lifetime. The project will also produce a microbiomechanical artificial mouth that can test composite-restored teeth under accelerated but clinically representative conditions, thus reducing the scope and costs of clinical studies by providing the initial screening of candidate materials. This will improve the longevity of composite restorations by 1) providing dental materials manufacturers with more clinically relevant assessments for product development, and 2) allowing dentists to make more informed and timely decisions on the selection of restorative materials and treatment plans.